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WRITING AND NAMING IONIC COMPOUNDS

WRITING AND NAMING IONIC COMPOUNDS. When atoms combine, it’s always in simple whole number ratios. The smallest unit of atomic combinations that retains the characteristics of the compound is a molecule.

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WRITING AND NAMING IONIC COMPOUNDS

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  1. WRITING AND NAMING IONIC COMPOUNDS

  2. When atoms combine, it’s always in simple whole number ratios The smallest unit of atomic combinations that retains the characteristics of the compound is amolecule

  3. The composition of a molecule can be represented in two waysaseither anempirical formula or a molecular formula C3H6 CH2 An empirical formula gives thesimplest ratioof atoms in a compound A molecular formula tells how many of each atom are present in the compound

  4. A remarkable feature of com-pounds formed from elements is that the properties of the reactant elements islost +

  5. In order to become more stable an some atoms find it energetically fea-sible to either lose or gain valence electrons. Atoms that lose e- are positive A.K.A. cation Atoms that gain e- are negative A.K.A. anion

  6. We tend to focus specifically on the loss or gain of the outer s, p, (A.K.A. valence e-) ,and sometimes the d e- of unfilled d sublevels). The valence e- an atom contains has a direct effect on the charge the atom develops as it forms an ionic bond. We have a list of the common ionic charges developed during ionic bonding.

  7. SOME COMMON CATIONS (Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements) +1 +2 +3 +4 Magnesium Lead (IV) Mg+2 Pb+4 Aluminum Al+3 Lithium Li+1 Vanadium (IV) Ca+2 V+4 Chromium(III) Cr+3 Sodium Na+1 Calcium Tin (IV) Sn+4 Iron (III) Cr+3 Potassium K+1 Strontium Sr+2 MONATOMIC IONS Vanadium (III) V+3 Rubidium Rb+1 Barium Ba+2 Cesium Cs+1 Cadmium Cd+2 Copper (I) Cs+1 Chromium (II) Cr+2 Silver Ag+1 Cobalt Co+2 Copper (II) Cu+2 Iron (II) Fe+2

  8. SOME COMMON CATIONS (Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements) +1 +2 +3 +4 Lead (II) Pb+2 Mn+2 Manganese (II) MONATOMIC IONS Mercury (II) Hg+2 Nickel (II) Ni+2 Tin (II) Sn+2 Vanadium (II) V+2 Zinc Zn+2

  9. SOME COMMON ANIONS (Note: the names of many of the ions include Roman numerals. These numerals are known as the Stock system of naming chemical ions and elements) -1 -2 -3 -4 MONATOMIC IONS Fluoride Nitride N-3 Oxide F-1 Pb-2 S-2 Chloride Cl-1 Sulfide Phosphide P-3 Bromide Br-1 Iodide I-1

  10. -2 -3 +1 C O N H P O -1 3 O H 4 4 There are also combinations of covalently bonded atoms that also have a charge called polyatomic ions Poly- means many, but we treat each of these polyatomic ions as a single unit with a single charge

  11. POLYATOMIC IONS

  12. POLYATOMIC IONS

  13. Today is all about combining these electrically charged ions together to form stable compounds. Reminder: when two atoms combine transferring valence electrons it is called an ionic bond. Oppositely charged ions attract each other and form an ionic bond that is electrically neutral, to establish a molecule that is neutral.

  14. Looking at the structure of salt shows that the attraction between ions is so great that many sodium ions and chloride ions become involved.

  15. The results of each ion being surrounded by several other ions allows the attraction between oppositely charged ions to be muchgreaterthan the repulsion between ions with thesame charge. The strong attraction between the ions, & the orderly arrangement in the crystal affect the properties of the compound.

  16. Cations & anions are pulled together in a tightly packed structure, giving each crystal a characteristic shape The simplest repeating unit of anions and cations is called a unit cell.

  17. Predicting the formation of ionic cmpnds We can predict the combinations of ions and the formation of their ionic formulas, knowing how ions interact We can have 2 different kinds of ionic compounds formed: binary or ternary

  18. WRITING IONIC FORMULAS There are a couple of rules to follow to make sure that the proper ionic formula is written.

  19. RULE #1 Ions will combine only inthe simplestwhole numberratiowhich cancels out the charge to form a neutral compound The sum of the ions’ charges must be zero 3(+1) + (-3) = 0 +2 + (-2) = 0

  20. RULE #2 The compound formula is ALWAYS written with the cation first then the anion. It’s better to be positive than negative  NaCl ClNa

  21. +1 -1 K I + +2 -2 Mg O + Some ionic compounds’ charges automatically cancel each other out. KI MgO

  22. What if we were forming ionic compounds with ions whose charges don’t add up to a charge of 0? How do we decide the proper ratio of cations and anions?

  23. +3 -1 Al Cl + +3 -1 AlCl Al 3 Cl + 3 =2 What if we had three chlorine ions for every one Aluminum ion?

  24. +3 -2 Al O & +3 -2 Al O 2 Al 3 O & 3 2 We need to find the ratio of ions that will make the charges cancel out to a neutral compound.

  25. We have a trick that will help us know the number of the ions to make a neutral compound. IT’S NOT A TRICK SO MUCH AS A SHORTCUT!

  26. +3 -1 Al Cl AlCl + 3 +2 -3 Ca P Ca P + 3 2 CRISS-CROSS RULE:

  27. Using polyatomic ions To write the formulas for compounds containing polyatomic ions, follow the rules for writing formulas for binary compounds, with one additional consideration. We add parentheses around the polyatomic ion when more than one of the ion is needed to develop the proper ratio.

  28. -1 OH + +3 Al Al(OH) 3 -2 +1 Na SO + 4 Na SO 4 2

  29. Ca+2 & O-2 Sn+4 & CO3-2 NH4+1 & SO4-2 Mg+2 & C2H3O2-1 Practice Writing Formulas CaO Sn(CO3)2 (NH4)2SO4 Mg(C2H3O2)2

  30. NAMING THEM • Most of the time you can name an ionic compound by • 1) Writing the name of the first element • 2) Writing therootof the name of the second element • 3) Adding-ideto the root

  31. NAMING THEM CaCl2  K3P  Al2S3 Calcium chloride Potassium phosphide Aluminum sulfide

  32. NAMING THEM Some of our metals have more than one ionic charge • We have to determine the charge on the metal • We then indicate the charge as a roman numeral

  33. NAMING THEM FeCl2  FeCl3 PbBr2 Iron(II) chloride Iron (III) chloride Lead (II) bromide

  34. NAMING THEM If the compound has a polyatomic ion in it 1) name the first element, including the roman numeral if appropriate 2) then name the polyatomic ion

  35. NAMING THEM Fe(OH)2  Ca3 (PO4)2  Na2SO4 Iron(II) hydroxide Calcium phosphate Sodium sulfate

  36. Strontium Nitrite  Sr(NO2)2 CuOH  Copper (I) hydroxide Lead (IV) phosphide  Pb3P4 NH4OH  Ammonium hydroxide Sodium carbonate  Na2CO3

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